SACRAMENTO — When the archives have been recovered and the names counted, the experts who made the decisions that climaxed with three dozen snapped steel bolts on the new Bay Bridge in March may fill an auditorium.

In a nearly three-hour grilling before the state Senate Transportation Committee Tuesday afternoon about the embarrassing engineering failure and a possible delay in the bridge’s scheduled Sept. 3 opening, Caltrans Director Malcolm Dougherty pointed to a list of teams populated with federal, state and private engineers, and academic engineering institutions including the National Science Academy, who were involved in the decision more than a decade ago.

“We had a lot of expertise at the table,” Dougherty testified. ” … The decision (to use the type of high-strength steel bolts that broke) was reviewed by material testing engineers, corrosion experts, consultants and the engineers of record at T.Y. Lin and Moffatt Nichol. There was experience using these bolts. It wasn’t risky.”

Committee Chairman Mark DeSaulnier of Concord and Sen. Anthony Cannella, R-Ceres, who is a licensed civil engineer, appeared unimpressed with the expertise argument and repeatedly asked for easier-to-understand explanations of who, what, when and where.

The senators hoped for answers, but the hearing plowed little new ground.

Instead, the leaders of the three agencies managing the construction project promised an update by the end of the month on who and how the bolts were selected, plus word on whether the repairs will be done in time to open the bridge as scheduled.

“My frustration stems from my inability to tell my constituents from Contra Costa and Alameda counties, who are a large portion of the commuters on that bridge, that it will be safe and that it is a value well spent,” DeSaulnier said. “Sitting here today, I don’t know if I would vote for that design given the benefit of hindsight.”

Caltrans, the California Transportation Commission and the Bay Area Toll Authority have been scrambling for more than two months to explain why 32 of 96 beefy steel anchor rods, 3 inches in diameter and from 17 to 24 feet long, broke in the massive pier east of the main span tower.

The disclosure has shaken public confidence and cast doubt on the structural integrity of the world’s largest single self-anchored suspension bridge just months before the $6.4 billion span was scheduled to open after more than 10 years in construction.

To help bolster public opinion, the agencies have asked and the Federal Highway Administration has agreed to review its bolt testing process and the proposed repairs.

Technically, engineers blame the fractures on a well-known phenomenon in high-strength steel fasteners subject to high levels of tension, where hydrogen atoms invade the spaces between steel’s orderly crystalline molecules and weaken it. The stronger the steel and the higher the tension, the more susceptible it is to hydrogen fractures.

Questions remain unanswered about why bridge designers chose to deviate from general industry and state warnings and use superstrong galvanized steel that is prone to this type of failure. That type of steel was used for 2,306 fasteners on the span.

The agencies are “hunting and pecking” for the written records of those decisions, Bay Area Toll Authority Executive Director Steve Heminger told the senators.

Many of the relevant documents were part of the first and subsequently aborted self-anchored suspension span bid that wasn’t awarded when a single contractors’ consortium responded with a bid for nearly double the state’s cost estimate.

“This would have gone a lot faster if the records were computerized and available,” Heminger said. ” … But we are getting closer. In our report (for the May 29 Toll Authority meeting), we will provide a very detailed report of who was there, what decisions they made and for what reasons.”

Heminger and his colleagues also explained to senators how they will retrofit the broken bolts — at a cost of up to $10 million — with a steel saddle secured with cables around the seismic stabilizers called shear keys. The shear keys help control sway during an earthquake.

Caltrans is also testing other steel pieces on the bridge, including rods in the main cable anchorage and elsewhere in the eastern pier. Technicians pulled a bolt from the bottom of the tower on Saturday for testing and will remove six pieces from the ends of the 3ï»¿1/2-inch diameter rods in the anchorage chamber, Caltrans spokesman Will Shuck confirmed.